1. Field of the Invention
The present invention relates to a construction machine such as a hydraulic excavator.
2. Description of the Related Art
In a conventional hydraulic excavator as a construction machine, both an engine and an exhaust system are accommodated within an engine room. The exhaust system comprises, concretely, an exhaust pipe extending from an exhaust valve of the engine, a muffler connected to the exhaust pipe, and part of a tail pipe extending from the muffler. Heat generated from the engine and heat generated from the exhaust system are accumulated in the interior of the engine room of the conventional hydraulic excavator, so that the internal temperature of the engine room becomes high.
As to the heat generated from the engine, engine cooling water is cooled by a radiator; besides, cooling air is introduced from a cooling fan, thus permitting an increase of temperature to be suppressed. On the other hand, as to the heat generated from the exhaust system, it causes an increase in the internal temperature of the engine room because any special cooling means is not provided. Particularly, the heat generated from the muffler is a primary factor of the increase in temperature because of a large surface area of the muffler which is constituted by an expansion chamber. Once the internal temperature of the engine room thus rises, the ambient temperature of the radiator rises, resulting in that the cooling efficiency of the radiator deteriorates.
According to the prior art, for solving such a problem, a cylindrical cover is mounted around the muffler, or the surface of the muffler is coated with a heat insulating material such as glass wool. However, when the conduction of heat reaches a steady state, heat is generated through the cover or the glass wool and thus the problem of increase in the internal temperature of the engine room has not thoroughly been solved yet.
It is an object of the present invention to provide a construction machine capable of preventing an increase in the internal temperature of an engine room and consequent deterioration in the cooling efficiency of a radiator which are caused by the generation of heat from an exhaust system, especially a muffler.
The construction machine of the present invention has an upper rotating structure formed by a revolving frame, an engine room formed at a rear portion of the upper rotating structure and in which are accommodated at least an engine, a radiator, and a muffler, a compartment formed within the engine room and in which the muffler is accommodated, and a vent portion formed in the compartment to make communication between the outside air and the compartment through an underside of the upper rotating structure.
In the present invention, the heat generated from the muffler is cut off in the compartment and is not transmitted into the engine room, and the outside air is introduced into the compartment through the vent portion, whereby an increase in temperature is suppressed. Thus, it is possible to prevent deterioration in the cooling efficiency of the radiator.
In the present invention, a bottom plate of the compartment may be a part of the revolving frame and the vent portion may be formed in the bottom plate. In this case, it becomes easier to form the compartment because the revolving frame constitutes the bottom plate of the compartment.
The bottom plate may have an opening formed as a cutout portion and an undercover attached to the opening, and the vent portion may be formed in the undercover. Alternatively, the vent portion may be formed by directly cutting out a part of the revolving frame. which constitutes the bottom plate. In the latter case, it is possible to attain the reduction of cost in forming the vent portion in the compartment because it is only forming apertures by cutting out the revolving frame that is required for the formation of the vent portion.
In the present invention, the radiator may be mounted on a top plate of the compartment. In this case, the top plate of the compartment can be utilized as a mount for fixing the radiator, thus permitting a compact arrangement of the engine, radiator, and exhaust system.
In the present invention, a fan which introduces the outside air forcibly into the compartment may be disposed near the vent portion. In this case, an increase in the internal temperature of the compartment can be suppressed more effectively because the interior of the compartment is ventilated forcibly by rotation of the fan.
In the present invention, an exhaust pipe which connects the engine and the muffler with each other may be accommodated within the compartment, or at least a part of a tail pipe connected to the muffler may be accommodated within the compartment.
Further, a heat insulating member may be affixed to the compartment, or the compartment may be formed by the heat insulating member. The heat insulating member may be a rigid polyurethane foam panel. In these cases, it is possible to enhance the heat conduction cut-off effect.
Further, a vent hole communicating with the compartment may be formed in a side wall of the revolving frame and the outside air introduced into the compartment from the vent portion may be discharged through the vent hole.